In recent years, from the viewpoints of the effective utilization of electrical energy and the like, SiC/GaN power semiconductor devices equipped with elements using SiC (silicon carbide) and GaN (gallium nitride) have been attracting attention (for example, see Patent Document 1.).
Since these elements can not only reduce the power loss greatly, as compared with the conventional elements using Si, but can also be operated with a higher voltage, a large current, and even in a high temperature reaching 300° C., they are expected to be deployed for use to which the application has been difficult with the conventional Si power semiconductor devices.
As described above, since the elements themselves (semiconductor elements) using SiC/GaN become operable under severe conditions as mentioned earlier, in order to protect these elements, a higher level of heat resistance than ever before has been required even for a semiconductor sealing material provided in the semiconductor devices.
Here, in the conventional Si power semiconductor devices, as a semiconductor sealing material, from the viewpoints of adhesive properties, electrical stability, and the like, those constituted of a cured product of epoxy-based resin composition as a main material have been generally used.
In such epoxy-based resin compositions, studies have been conducted to improve the heat resistance of the semiconductor sealing material obtained by using such resin compositions by employing techniques so as to increase the crosslinking density by lowering the epoxy group equivalent of the epoxy resin serving as a constituent material or the hydroxyl group equivalent of a curing agent (phenol resin curing agent), or to configure the structure connecting between these functional groups (epoxy groups and hydroxyl groups) into a rigid structure, or the like.
However, even by such studies, in the semiconductor sealing materials obtained by using the epoxy-based resin compositions, the heat resistance thereof was not necessarily improved sufficiently.
Accordingly, use of a cured product of a resin composition containing bismaleimide and benzoxazine as a semiconductor sealing material instead of the epoxy-based resin compositions has been considered (for example, see Non-Patent Document 1).
Although it is possible to improve the heat resistance by using a resin composition having such a configuration, as compared with the epoxy-based resin compositions, the actual situation is that further studies have been currently conducted on a resin composition capable of forming a semiconductor sealing material having heat resistance suitable for the use conditions of the Si power semiconductor devices.